Scharnhorst’s Last
Message?

The ciphertext message below is suspected to be the last message from the German
battlecruiser
Scharnhorst. The message was intercepted by one of the the radio
officers, D. Rough, on board the English battle ship Duke of York in the
evening of 26 December 1943. The message, which was transmitted in Morse code,
was received on a HRO receiver and written out on the customary W/T Red Form.
The Red Form has been found among the papers of Edward Thomas who was the
intelligence officer on board the Duke of York. Today the Red Form is
owned by the collector Mr. Colin Waghorn and I am grateful for his permission to
publish this historical document here.

In December 2007 Geoff and I were contacted by the
Bombe Rebuild Project to hear if we could help with breaking this message.
The rebuilt Bombe at BP did not have the necessary Naval Enigma rotors and they
wondered if our E-Breaker program would be able to do the job. Unfortunately, we
don’t have a Naval Enigma version of this program and both Geoff and I were too
busy with work and other tasks to envisage starting yet another codebreaking
project. We kindly asked for permission to give the message to Dan Girard, who
since then has been trying to break the message with a Bombe simulator using
cribs from the plaintext message. Here is a report on his attempts so far:

I’ve had no success with the Scharnhorst message. I’ve tried the
vierneunneunzwo crib in various positions; also steuereauftanafjord,steuereaufjtanafjordj,steuerenachtanafjord,steuerejtanafjordjan, etc.;
and, at the beginning of the message, the signatures vvvjscharnhorstj,vonvonjscharnhorstj, and vonvonscharnhorst. I’ve also tried
mueckevvvjscharnhorst as a crib. The other urgency codewords, “biene”
and wespe, and the variants bine, “mucke” and muke all result in crashes
when placed before the signatures, so I didn’t try those.
Nothing has worked. Of course, until the message is broken there’s no way of
knowing whether this was due to garbled ciphertext letters or because the cribs
were either incorrectly aligned or wrongly worded.

A good account of what happened during the Scharnhorst battle has been
given by Patrick Beesley in his book
Very Special Intelligence.
Here is an extract from page 216 that describes the final hours of the
battlecruiser Scharnhorst
and the transmission of its last message:

At 4.17 p.m., Duke of York gained radar contact with the enemy and at
4.50 opened fire. Once again
Scharnhorst was taken by surprise. At 4.56 she signalled to Gruppe
Nord-Flotte: ‘Most Immediate. 72 degrees 39 North, 26 degrees 10 East. Heavy
battleship. Am in action.’ Bey evidently mistook some of Burnett’s cruisers for
battleships because at 5.22 he signalled that he was ‘surrounded by heavy
units.’ The situation soon became hopeless. At 6.02 a signal went off to
‘Admiral of the Fleet and the Commander-in-Chief. Scharnhorst will ever
reign supreme,’ and this was followed at 6.25 by one to Hitler, ‘We shall fight
to the last shell.’ Scharnhorst’s last signal was made at 7.25, stating
that she was steering for Tanafjord at 20 knots. It seems unlikely that she was
still capable of this speed because, shortly before she had reported it as only
15 knots, and within another twenty minutes, after repeated hits from Duke of
York’s 14-inch guns, from the lesser armament of the cruisers and from
eleven of the many torpedoes fired at her by the British destroyers, she sank.
Despite every effort only thirty-six survivors could be rescued.

As explained in Very Special Intelligence most of the messages from
Scharnhorst and Admiral Northern Waters were quickly broken and decoded at
Bletchley Park (BP). The messages were enciphered on the 3-rotor Naval Enigma
machine M3 and most of them were using the
Allgemein (general) settings from the Enigma key Heimisch.
Heimish, later renamed Hydra and called Dolphin by BP, was the Enigma
key used by U-boats and surface ships in German home waters, in the North Sea,
and the Atlantic. A few of the signals were enciphered using the
Offizier setting of the Heimisch key. These signals were usually
decoded but with a delay of two to three weeks. One Offizier signal that
was transmitted on 18 December 1943 and that instructed the Battlegroup with
Scharnhorst to take ‘preparatory measures so that departure would be
possible at any time’ seems to have been broken with a delay of only two days.

The Red Form shows two messages labeled 1) and 2). The first message seems to be an emergency warning to
everybody (An Alle) that a KR KR message – Kriegsnotmeldung (war emergency message) was to
be expected. The regulations for the use of a war emergency message was very strict: Kriegsnotmeldungen dürfen nur bei unmittelbarer Gefahr und höchster Notlage für Schiff und Besatzung
abgegeben werden — War emergency messages must only be transmitted when immediate danger and
the highest emergency exist to ship and crew. The transmitting station uses the callsign ANÄ, which is
an Umlaut callsign — Umlautfunkname. These callsigns, which could not be enciphered, were usually given
to fixed land stations. If it was exceptionally given to Scharnhorst for this engagement is not
known. Nor is the meaning of LA understood. It could be a frequency reference as the German naval
frequencies were given two letter designators, however the frequency lists I have access to shows
la as 109 kHz and the frequency 6475 kHz is not listed.

The second message is the suspected last message from Scharnhorst. It starts of with some
priority dots and then gives the time of origin, 1925, and the number of cipher groups, 21. A quick
look at the message shows that it has 24 groups. If the error in group count is due to the cipher
operator on Scharnhorst or the radio operator on the Duke of York is impossible to say.
The message is in the standard Naval Enigma format with the two first 4-letter groups being respectively
the Schlüsselkenngruppe (Cipher Indicator Group) and the Verfahrenkenngruppe (Procedure Indicator Group),
both being repeated as the two last groups of the message. For further information please see the General
Naval Enigma Procedure –
Der Schlüssel M Verfahren M Allgemein.

As can been seen from the BP decode the last message from Scharnhorst was decoded on 13 January 1944,
almost three weeks after it was transmitted. What does this mean? The most obvious reason is that this
message was transmitted in the
Offizier key and BP had difficulties in breaking this key. As the battle was over there would not
have been a great urgency in breaking the message and this could also account for the delay. Another
possibility is that BP’s intercept stations failed to receive this message and that they first got a
copy after the Duke of York was back in harbour. In this case the decoding of the message could
also easily have been delayed by two, three weeks.

Message Broken

The M4 Message Breaking Project started a break on this message on 27 May 2008 at 22:39:21.
Less than 24 hours later, on 28 May 2008 at 18:16:21, the message was broken. The German plaintext does
indeed correspond to the English plain text in the BP teleprint. The raw German plaintext is:

Dan Girard was indeed only a hair’s breadth from breaking this message with his Turing Bombe simulator.
Here is his story:

Since steuerejtanafjordj is one of the cribs I had tried with my bombe simulator, it’s obvious that I
must have made a mistake somewhere; and sure enough, on re-checking the menus I had drawn up for this crib,
I find that I had misread one of the links from the diagram I had made. I had drawn up seven different
menus from the crib, in order to allow for different turnover possibilities; and it was just my bad luck
that the only one of the seven on which I made the mistake was the one which had the right turnover
assumption. This is embarrassing!
I’ve checked on the vierneunneunzwo crib, and it turns out that one of the positions I tried it in was
the correct one; but unfortunately for me I had assumed that since there was a comma between 4992 and
speed in the translated decrypt, there would be one in the German plaintext, as vier neun neun zwo y
fahrt...; and I included the y in the crib. I’ve just re-run the relevant menu, omitting that link,
and found that it would have worked.

This shows yet again that selecting cribs and constructing menus is indeed more of an art than a
science; an art where the codebreakers at Bletchley Park were the real masters. We should all stand
in awe of their achievements.

Closing the circle

Yesterday, 30 April 2010, I received the following good news from Paul Kellar at BP:

Hello everybody

This is the last link in the chain from the original Red Form.
We have made the rotors 6,7 and 8 for our Typex (which, as you know, we have previously
converted to behave like an Enigma, as they did at BP).
This would output both the original and the decrypt on paper tape which, like a telegram
was gummed to a message form. It groups letters by fives, as you see.
Using the settings from Frode's group we have decoded the original message to reproduce
the decoded output as seen 66 years ago.

Thanks, everybody!

Regards
Paul

And this is how the Scharnhorst messages would have looked like when it was decoded at BP in
January 1944.

Acknowledgments

We should first of all like to thank the Bombe Rebuild Team who immediately thought of us when they
realized they were not in a position to attack this message. Of the team we should like to particularly
thank John Harper, Paul Kellar, Mike Hillyard, and John Borthwick, who sent us the copies of the Red Form
and the teleprint with the BP Decode. Special thanks goes to John Gallehawk, who through his thorough and
persistent search in the National Archives at Kew discovered the BP Decode teleprint. Futhermore, we are
most grateful to Dan Girard who stepped into our shoes to do the work Geoff and I had neither the time
nor the energy to do. Finally we should like to thank the owner of the Red Form, Colin Waghorn and his
partner Dr. Rebecca Hill. And as always we are most grateful to have Ralph Erskine as our friend and
mentor, who is always there to hold our hands when the sea gets rough.